Pseudowire (PW) is a mechanism for carrying critical elements of one emulation service from one provider edge (PE) to another over a packet switched network (PSN). Multiple types of services are emulated using one tunnel on the PSN. The multi-protocol label switching (MPLS) tunnel is commonly used in the PSN.
Referring to FIG. 1, a seamless MPLS network based on pseudowire emulation edge-to-edge (PWE3) is illustrated. A terminating provider edge (T-PE) (for example, an access node) uses static routing. A commonly used access node is a digital subscriber line access multiplexer (DSLAM) or an optical network unit (ONU).
The user-facing provider edge (U-PE), which is also referred to as a router, directly connected to the access node allocates the static routing of the access node to an intermediate system to intermediate system (ISIS) domain. The T-PE allocates outer label switched path labels by using Label Distribution Protocol (LDP). The router allocates inner LSP labels by using Border Gateway Protocol (BGP) between the U-PEs.
In a seamless MPLS network, the PW is an end-to-end single segment PW (SS PW). To be specific, multiple-segment PW is not used from the access node on one end of the network to the access node on the peer end of the network. In addition, the access node further supports a flow label, for balancing PW load. Generally, the T-PE needs to support three layers of labels (an outer LSP label, a PW label and/or a flow label), and the U-PE needs to support four layers of labels (an outer LSP label, an inner LPS label, a PW label and/or a flow label).
During the implementation of the present invention, the inventor finds that the prior art has the following problems:
In the seamless MPLS network, an end-to-end MPLS architecture is used. MPLS is extended to the access node. It is a critical issue during MPLS network construction that how the U-PE supports splicing of the outer LSP of the access node and the aggregation network and the core network.
In addition, the number of access nodes such as the ONU and DSLAM is large. Therefore, the costs must be low. For this reason, the ONU and DSLAM are generally Layer 2 device only. However, to support MPLS on the access nodes, all ONUs and DSLAMs need to upgrade the control plane to Layer 3, and must support a routing protocol, an MPLS label allocation protocol, and a PW label allocation protocol. This increases the complexity of the ONUs and DSLAMs, for which the costs is increased and scalability is poor.